Summary
A UV sensitive mutant of Saccharomyces cerevisiae, rad 1–3, considered to be blocked in a repair process of the excision-resynthesis type, exhibited in synchronized cultures, cyclic variations to UV-induced lethality comparable to those of the wild type strain. That is, the G1 phase was the most radiosensitive and G2 the most radioresistant.
A mutant which is deficient in UV-induced intragenic recombination (rec 5), also exhibited cyclic variations in radiosensitivity although the pattern of the response was strongly modified as compared to that of its original wild type: there was a progressive increase in radiosensitivity during the G1 phase which is never observed in a wild type strain.
The double mutant rec 5, rad 1–3 also exhibited the same type of cyclic responses in radiosensitivity as rad 1–3 and wild type strains, but the magnitude on the fluctuations was diminished due to a decrease in resistance during the G2 phase.
Our results show that the repair process of the excision-resynthesis type, which is blocked in rad 1–3, would act very efficiently on UV-induced lesions and constantly throughout the cell cycle. The repair mechanism involved in intragenic mitotic recombination (rec 5 strain) would mainly act during S and G2 phases.
The response of rec 5 rad 1–3 mutant showed that the two repair mechanisms refered to would not be the sole mechanisms involved in the expression of cyclic variations in lethality.
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Communicated by F. Kaudewitz
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Chanet, R., Heude, M. & Moustacchi, E. Variations in UV-induced lethality and “petite” mutagenesis in synchronous culture of Saccharomyces cerevisiae. Molec. Gen. Genet. 132, 23–30 (1974). https://doi.org/10.1007/BF00268227
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DOI: https://doi.org/10.1007/BF00268227